A waveguide antenna is an antenna that directs RF energy from an air medium into a waveguide, where the RF energy is conducted through the waveguide interconnections or picked up by the coaxial interface and later transmitted through the coaxial assembly. Today we come to know about waveguide horn antenna.
A waveguide horn antenna is an aperture antenna that utilizes a gradient transition from the conductive interior of the waveguide to the end of the horn, causing the waveguide ports to undergo an impedance transition that matches the free space. This is of course frequency dependent and the gradient of the waveguide horn antenna has an effect on the antenna performance. Waveguide horn antenna can be used with any type of waveguide, square, circular, or elliptical.
The shape of the horn of a waveguide antenna can also vary depending on the desired performance, i.e., directivity, gain, and antenna orientation map. The way the horn is unfolded affects the directivity, gain, antenna direction map, and bandwidth of the waveguide horn antenna. Horns can be unfolded as a single slope, curvature, or even a nonlinear horn with ripples or other features. Typically, a wider horn will have a wider beamwidth, but will sacrifice gain or directionality to accomplish this.
Modifications to the way the horn opens are made to correct for undesired antenna performance. Additional dielectric structures or conductive features can be added to the waveguide horn antenna shape to change the impedance and bandwidth characteristics of the horn. An example of this is a broadband waveguide horn antenna, which can be made to have a much higher bandwidth than a typical cone or tapered horn antenna.
Within a waveguide horn antenna, the waveguide conducts a planar electromagnetic wave that gradually transforms into a free-space propagating curved wave front. In rectangular antennas, the waveguide pattern is usually TE10 or TE01 with a curved wavefront. Fan horn antennas emit cylindrical wavefronts and conical horn antennas emit spherical wavefronts. The flare of the horn affects the gain, beamwidth, and directivity of the antenna response. The wider the flare, the wider the beamwidth and the lower the directivity and gain. Dielectric lenses can also be added to the end of the waveguide to convert a planar wavefront into a curved wavefront. These horn lens antennas can exhibit higher gain or directionality than typical horn designs.
The waveguide horn antenna exhibits high gain and directivity, as well as high power handling and relatively high efficiency. This is why waveguide horn antennas are often used in high power applications and at very high frequencies. Waveguide horn antenna antennas are often found in test and measurement facilities and are also deployed in sensing and satellite communication applications.
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